Peak Sun Hours in Iowa
2026 NREL PVWatts v8 Data
Iowa averages 4.75 peak sun hours per day, ranking #32 of 51 US states and DCfor solar potential per NREL's PVWatts v8 model. That puts Iowa 5% below the US average of 4.98 PSH.
Monthly Peak Sun Hours in Iowa
Iowa's solar resource peaks in June at 6.66 peak sun hours per day and bottoms out in December at 2.67. That December figure is the one that matters most for sizing.
What 4.75 Peak Sun Hours Actually Means
A peak sun hour represents one hour of solar irradiance at 1,000 watts per square meter. Iowa gets far more daylight hours than 4.75, but the sun isn't always at peak intensity. Peak sun hours compress a full day's variable sunshine into an equivalent number of full-power hours.
In practical terms, 4.75 PSH means a 400W solar panel in Iowa produces about 1.43 kWh per day after real-world losses.
Solar Production in Iowa
Benchmarks: U.S. avg 4.98 · Phoenix 6.54 (highest) · Seattle 3.95 · Anchorage 3.17 (lowest). Above ~5.5 = sunny · 4.5–5.5 = average · below 4.5 = cloudy.
Tap to see sensitivity analysisSensitivity analysis
| Scenario | Value |
|---|---|
| Low (-20%) | 1.1 kWh |
| Expected | 1.4 kWh |
| High (+20%) | 1.7 kWh |
Your daily production scales linearly with both panel wattage and peak sun hours. A 10% change in either input changes your result by 10%.
Worked Examples for Iowa
| System Size | Daily kWh | Monthly kWh | Yearly kWh |
|---|---|---|---|
| 3 kW | 14.3 | 428 | 5,201 |
| 5 kW | 23.8 | 713 | 8,669 |
| 10 kW | 47.5 | 1,425 | 17,338 |
Using Iowa's annual average of 4.75 PSH. Winter production drops ~30%; summer runs ~25% higher.
How Iowa Compares
The US average is 4.98 PSH per day, so Iowa sits 5% below the national average.
| State | Annual PSH | Rank |
|---|---|---|
| Pennsylvania | 4.79 | 30 |
| Montana | 4.76 | 31 |
| Iowa | 4.75 | 32 |
| Massachusetts | 4.7 | 33 |
| Rhode Island | 4.7 | 34 |
Best and Worst Months
June is the best month at 6.66 PSH. A 5 kW system produces roughly 33.3 kWh per day — nearly 2.5x what it produces in December.
December is the weakest month at 2.67 PSH. Size your system for December to ensure year-round coverage.
Is Solar Worth It in Iowa?
With 4.75 PSH, Iowa has good solar potential. The federal ITC covers 30% of installation costs through 2032.
Methodology & Data Source
NREL PVWatts v8 / NSRDB, fetched April 2026 for Des Moines (41.5868°N, -93.625°W). 1 kW reference system, fixed roof mount, 20° tilt, 180° azimuth, 14% losses.
Source: NREL PVWatts v8